Table 1.

Fitting parameters for the analytical models (analytical model (new) is from this study, analytical model (old) is from Zheng et al (2007)) for the specific condition (an unmodulated 250 MeV proton beam incident upon a medium-sized closed aperture. The aperture was closed for both in-air and water phantom cases). Dashes indicate that parameters were not used in the given situation.

	Analytical model (old)		Analytical model (new)
Parameter	Air	Water phantom	Air	Water phantom
diso	33	33	33	33
p1	1.30	2.0	1.0	1.0
p2	–	–	1.45	2.0
C1	–	–	0.20	0.24
α1	–	–	–	0.01
α2	–	–	–	0.017
σ1	–	–	15.85	9.18
σ2	–	–	820.34	1011.07